OVERALL OPERATING CHARACTERISTICS OF SUPERCONDUCTING CURRENT-FEEDER SYSTEM FOR THE LHD

摘要

A superconducting (SC) current-feeder system is used as the current transmission lines for the LHD. It consists of nine SC bus lines with total length of 497 m and nine pairs of gas-cooled current leads. The cooling process is automatically switched from forced-flow of two-phase helium to pool boiling, when faults happen. Liquid helium consumption of the innermost tube of the SC bus line was negligible, because the liquid helium in the second inner channel absorbed the heat load of 0.34 -0.42 W/m. Mass flow rates of the current leads could be controlled in constant values, whenever the pressure in the recovery line reached up from 0.106 MPa to 0.133 MPa. The allowable current carrying time on the fault protection mode is expected to be longer man 30 minutes of the design value. We successfully demonstrated mat the SC current-feeder system with high current capacities was reliable and safe, and was useful for the SC experimental fusion device.